This is a demonstration of measuring the axle hub runout on a vehicle this round hub right
here is what centers the wheels at least the factory wheels on most vehicles and if it is
kind of wobbling up and down as its rotating as you drive down the road then that can lead to a
first order tire speed related vibration and a first order vibration is anything that creates
one shake or one disturbance per revolution of whatever that part is so a first order tire
speed related vibrations create one shake per revolution so we are going to hook up a dial
indicator to measure this hub for roundness but the problem we have here is there are studs in
the way so we can't just simply come in with a dial indicator on this surface right here
because as we rotate the axle shaft around the studs would hit it so instead we have to use
an adapter here with a another dial indicator and this adapter I refer to as a teeter-totter
adapter I guess I've never actually looked up its official name I think it's actually called
an inside hole adapter for a dial indicator but you slide the dial indicator into this adapter
and align the plunger of the dial indicator up with this little teeter-totter looking piece and
we have a one-to-one ratio of the teeter-totter so however far I pushed down over here on the
right the plunger will be pushed up on the left by the same amount so if I push down
with 10 thousandths of an inch the other side will go up 10 thousandths of an inch and then
we can read in thousandths of an inch on the face of this dial indicator and what we're going to do
is hook this up to a the dial indicator stand to where we can read inside and this is this is
long enough that it's going to miss the wheel studs but we're gonna come in underneath with
this little adapter and it'll push up so I'm gonna have it mounted just like this and I'll
have to reposition the camera so you can see the the setup and the dial indicator measurement but
this is the only way I've been able to figure out how to get in and measure how round this
particular hub is so let me get the dial indicator and the camera set up and repositioned and we will
go from there okay I've got the dial indicator set up with the inside hole adapter the part I
called the teeter-totter adapter reaching in and measuring the in or the outside diameter of this
hub we're not measuring the diameter but we're on the outside circumference of this hub and I'm
going to zero the dial indicator at this point that doesn't mean that's the high spot or the
low spot that's just a point where I'm going to start comparison and we're gonna have watch
to see how high it goes above zero and how far goes below zero and that's our totally indicated
reading that we're looking for here so here we go oh whoops that's going the wrong way let's
try that again the little teeter-totter adapter has some lateral movement so you've got to always
rotate in the same direction so let me hit zero that again here we go okay so here we go zero
got a hat one maybe two and back to zero so we had about two thousandths of an inch runout
there's still a little bit of surface rust that I was in unable to clean up with the sandpaper but
two thousandths of an inch three is the maximum allowed so the ones I've seen like I said that
her in really good shape have no runout it's just dead zero or or just a tiny bit above but
less than one thousandth of an inch this one has to but that includes the some of the surface rust
it's still less than the three specification so we're in good shape now if you add more
than the three thousandth of an inch then you'd have to replace the axle shaft itself because
that would cause the will entire assembly to be moving up and down as you drive down the road so
this is one of two measurements that you do on an axle shaft for run-out the other measurement
is going to be on this outer flange for run-out for the lateral work runout side to side so this
is vertical runout on this hub the up-and-down runout now we're gonna measure lateral which is
out here for side-to-side runout so let me get the dial indicator Center for that and
we'll measure that next okay I've now got the dial indicator hooked up with the roller roller
tip and we're gonna measure the runout of this axle flange surface here if it has runout then
it'll cause the wheel and tire assembly to wobble back and forth that's lateral run-out
which can also cause a first-order speed-related vibration so let me zoom in here just a little
bit we can watch the dial indicator that zeroed once again we're just looking for
totally indicated reading of runout so how high does it go above zero how far does it go below
zero and let's see what we have this should also not exceed three thousandths of an inch
looks like we got up close to three but did not exceed the three thousands if it did exceed three
thousand so you may have a bent axle shaft maybe the car your truck was in an accident or they've
hit a really big pothole or a rock or a curb or something with their tire and wheel assembly that
can bend this axle face here or the axle shaft itself so okay there is one more measurement
on the this axle flange area that we need to consider and that is that it's the brake rotor
that slides over these wheel studs and sits on this surface and so the surface rust on the back
and the brake rotor can cause the brake rotor to have excessive run-out in the same area and that
could cause the wheel to have excessive or runout also I've also seen where the flange area of the
rotor that slides over these wheel studs is not equal thickness all the way around and so if you
do this same check with the dial indicator after putting the brake rotor on you're going to get a
different reading now we measured close to three thousandths of an inch runout on this axle shaft
let's take this same measurement but with the brake rotor installed and see if there's any
difference if there is then it could be surface rust contributing or unequal thickness of the
flange where it slides over the studs all right we're looking at the back of the brake rotor and
you can see their surface rust there but it's in a pattern that matched how it was removed from the
vehicle and you'll notice that on the wheel studs here that I put a paint mark on this wheel stud
and there's a paint mark here on the brake rotor where that wheel stud went through and so we're
looking to have the those two matched up when you put that on that way you were rust pattern
on the back will match how it was when you took it off now I know not everybody cleans up that
surface rust every single time that they take a brake rotor on or off and put it back on and
you can minimize the amount of lateral run-out caused by not cleaning that up by making these
marks before you disassemble it so let me get the dial indicator set up we're going to measure the
run-out on this surface now where the will rides but through the brake rotor itself and of course
I'll put some wheel studs or lug nuts on here to hold it down okay now got the dial indicator
with the roller contact out here on the outside of the the brake rotor hub area I can't come in
any closer because of this hole here in the brake rotor and so I'm going to have to measure it out
here but we're gonna still hold to the three thousandths of an inch maximum run-out but
realize the farther away you get from the center of the axle the more run-out you're going to have
three thousands out here would be less than three thousand sinned here it's like a piece of pizza
it's wide out here and pointed so much smaller on the inside there so let's rotate this around
and see how much we runout we have with with the brake rotor on now remember we had a little less
than three thousand s run-out without the brake rotor and so here we go Ron zero there lets you
that is a lot of runout wow that's that's a lot more than I thought let's let's look at
that again okay so we're at zero way about three under zero we go all the way around past zero
that's 50 thousandths 55 60 about 63 thousandths of an inch plus the two that went below the zero
to give us right there 65 thousandths of an inch lateral run-out the wobble back and forth now why
would it be that much well I'm measuring out here on this outer edge rather than in here a little
closer where the I mean I'm an inch away from where the wheel rides on the brake rotor I'm an
inch farther out but this rotor could be damaged this is a training vehicle and so who knows who's
been pounding on it with a hammer to get it off rather than putting the screws in or the
bolts in to pull it off or to push it off with the threaded bolt pushing against the axle flange for
maybe somebody's hit it with a hammer and bent it but this would if it if well I could not if since
it has sixty five thousandths of an inch ladder or runout here imagine how much more that's going to
be out here at the edge of the tire so it'll be interesting to put the tire and we'll assembly
on here next and see how much lateral run-out we have in the tire we'll assembly so this has
been a demonstration of measuring runout on axles and we've measured the hub runout the axle flange
rrunout under the brake rotor and now the flange runout on top of the rotor and we've seen that
it's way out of specification on this one by the way another reason that could be that much is miss
machining of this rotor I've seen once again where the thickness of this rotor is not equal all the
way around but let's also not forget surface rust there could be surface rust on the other
side that's contributing to that so it would be interesting to clean all of that up and see how
much it reduced the run-out but if you just slap it all together like this you're going to expect
to have some lateral run-out as you drive down the road and vehicles are less susceptible to
lateral run-out this side to side then they aren't a radial run-out which is the up and down run-out